The timer lsp-refresh command configures the refresh interval of LSP.
The undo timer lsp-refresh command restores the default value.
By default, the refresh interval of LSPs is 900 seconds.
| Parameter | Description | Value |
|---|---|---|
| refresh-time | Specifies the LSP refresh interval. | The value is an integer ranging from 1 to 65534, in seconds. |
Usage Scenario
Link states on an IS-IS network are synchronized by the flooding of LSPs. The flooding of LSPs is a mode in which a router sends an LSP to its neighboring routers and the neighboring routers send the received LSP to their respective neighbors except the router that first sends the LSP. In this manner, the LSP is flooded among the routers of the same level. By this flooding, each router of the same level can learn the same LSP information to synchronize its LSDB.
The flooding of LSPs needs to be refreshed periodically, because when a device generates the system LSP, it fills in the maximum lifetime for this LSP. After other devices receive this LSP, the Keepalive time of the LSP is reduced continuously. If a device does not receive any more refreshed LSPs and the lifetime of the LSP is reduced to 0, the LSP will be deleted 60s later if no more new refreshed LSPs are received.
The timer lsp-refresh command configures the refresh interval of LSPs to keep the LSPs valid and control the network convergence speed.
Prerequisites
Before running the timer lsp-refresh command, run the isis command to create an IS-IS process.
Configuration Impact
If the refresh interval of LSPs is configured too short, the LSPs will be refreshed frequently, which causes excessive usage of bandwidth; If the refresh interval of LSPs is configured too long, the network cannot receive information about changes of link states in a timely manner.
Precautions
The refresh interval of LSPs must be at least 300 seconds shorter than the maximum Keepalive time of an LSP specified in the timer lsp-max-age command. In this manner, new LSPs can reach all routers in an area before old LSPs expire.